Electric plug



0c1. 18,1927. n l 1,645,650

T. w. KIRKMAN.

ELECTRIC PLUG Filed April llI 1925 Patented Oct. 18, 1927.

PATENT/orales.

Application med April 11, 1985. 88H81 lo. 82,178.

This invention relates to electrical connections and particularly to a )ack plug for use lin telephony especially adapted for use with radio broadcast receiving sets.

In this field there is ardemand for a )ack plug to which the terminal` tips. of head phones or loud speakers may b e quickly and easily attached, and from which they may be as quickly removed. The invention provides a plu having cam-actuated clamping means whic engage the terminals frictionally and whichmay be readily actuated to grip the terminals very tightly or to re-..

lease them at will.

Preferred embodiments of the invent1on are illustrated in the accompanying drawin in which iig. 1 is a side elevation of the complete plu with the cable attached;

Egig. 2 is an edge elevation of the same; Fig. 3 is an enlarged view similar to Fig. 1, with the partsvbr'oken Iaway to show the internal construction;

Fi 4 is a view similar to Fig. 3, showin t e parts inrtip releasin position;

iig. 5 is a section -on t e line 5--5 of Fi 3 Fig is a fragmentary view showin the construction of one of the contact mem ers;

Fig. 7 is a view similar to Fig. 4 and 1llustrating a modiiied form of the'device.,

The contact elements of the plug consist,

`as is usual in the art, of a tubular sleeve 11 and a head 12 spaced apart by a'bushing 13 which connects them mechanically, but which insulates them electrically from each other. The head 12 is carried on a tongue "14 which passes throu h the bushing 13 and fits tightly therein. ear the up er or rear end of the tubular sleeve 11 it is urther sustained by an insulating bushing 1 5, and be-` yond this bushing it is formed with an oli'- set 16 and a normally bowed contact member 17 which appears straight in Fig. 3 because it is there shown as held under cla.mp ing pressure. The tubular sleeve 11 is simi-y larly provided with an extension having an offset portion 18 like the. ofi-set in the tongue 14 and terminating in a bowed contact member 19 like the contact member 17 and opposed thereto.

The upper or rear end of the tubular sleeve 11 is xed in an insulating head .20. The exact mode of mounting is not material, but the referred way is to mold the head 2O onto t e sleeve 11 so that a close and permanent connection is assured. The head 20 is of generally circular contour and is pro- .vided with an annular 'de member 21 which may conveniently tgd the form of an up-standing rib, as shown. At its middle the head 20 is formed with a recess 22 along the margins'of which the off-sets 16 and 18 extend, the recess bein so formed that the extremities of each og the bowedl contact members 17 and 19 seat against straight supporting faces 23 with theiri intermediate vportions bowed outward therefrom. Con.

centric with the guide21 is a hole to receive a pivot connecting .member for the combined cover and clamping cam hereafter described.

There are two resilient clam in members 24 which are mounted in the head 20 and which may conveniently `be xed therein durin the molding operation. The free ends of t e members 24 lie in o posed relation to the bowed contact memh 19. Approximatel vals between the -c amping members 24 yand their respective opposed contact members 17 and 19 are two apertures 25 formed in the head .20 through which the cord tips of a telephone cable 27 may be inserted.

A cover disc 28, also of generally circular' contour, is mounted yto turn on the head 20.

It is held by means of a` bolt 29 and `is guided by a circular groove which receives the rib 21. The purpose of the rib 21 and the coacting groove in the'cover disc is to center the cover disc 28 on the head 20 independently of the bolt 29. Thus the bolt 29 merely holds the arts in assembled relation, the'rib relieving the bolt of lateral stresses.. p The cover disc 28 is likewise of insulatin 'material' and carries an integrally form cam member 30 which projects into the recess 22 and is positioned between the resilient clamping members 24. It may be given any form suited to the accomplishment of its intended purpose, which is simultaneously to force the two clam ing members 24 outward as the cover 28 is rotated on the head 20. Inthe form chosen for illustration (see Fig. 3) `the cam is formed with two opposed fiat surfaces, and between these, two curved surfaces of progressively varying radius.

.The cam is symmetrical with respect to a line so that it will clamp when turned in either direction.

When the fiat surfaces are beneath the clamping members 24, these swing inward ers 17 andv aligned with the intertit) because of their inherent resilience. In this position the cord tips maybe readily 1nserted or withdrawn. After they have .been inserted, the cover 28 is rotated in either direction relatively to the head 20 so as to cam the clan'iping members 24 apart. This forces the clamping members 24 outward pressing them against the cord tips 26 and clamping these tips in place. Under such pressure, the bowed contact members' 17 and 19 are flattened out. The purpose 1n bowing them is to give some resilienceto the clamping action and to col'npensate for the wear of the cam 30 which may occur after lon continued use.

Ogbviously the clamping members 2e might omitted, in which case the cam 30 would clamp directly against the cord tips 26. This lconstruction is inferior for the reason that the` cam would soon be worn under the contact with the cord tips. The clamplng members 24 afford a much larger arca of contact with the cam and relieve it from the severely localized pressure to which it would otherwise be subjected.

A comparison of Figs. 3 and 4 will show that the contact members 1T are normally bowed, but thatin the position of maximum clamping pressure they are entirely flattened out.

, VYhile I prefer the use of a com mounted on a rotary cover, some of the advantages of the invention can be secured with a slightly different construction, for example, that shown in Fig. 7 Here the cover disc 28 is iixedly mounted on the' head 2() by means of Screws 3l, and the cam 30 is en- 'tirely omitted, as is the bolt A plunger 32 is mounted toy slide transversely through the head 2O and cover disc 28 and carries Within the reeess22 a tapered or conical cam member 33 which directly engages the resilient clamping members 24. .By pushing the -iiunger 32 in one direction, the cam. 33 erces the clamping' members 2.1i apart to ciamp the cord tips 26. In such clamping iosition the cam is retained by friction.

ien t plui'iger 82 is pressed inthe opposite direction, the clampingr members 24 are released to free the cord tips 2G.

The construction shown in Figs. l to 6 is preferred for the reason that the use o' a rotary cam permits a little greater range of movement of the cam, and hence a more gradual clam ing action. Furthermore, this embodiment is subject to less risk of accidental release of the cord ti )s since there is substantially no tendency o the cap to rotate on the head under light impacts such as are likely to occur in use.

nti-enano While I have described the construction of the arieus parts in some detail, the invention obvious y is capable of various mechanical expressions, and I do not imply any li'nitation to the specific construction except to the extent specified in the claims.

'Vhat is claimed iS:

1. In an electrical connecting plug, the combination of contacts; clam ing means for connecting the terminals o an electric euble'in conducting relation with said contacts; a body housing said clamping means; a cover rotatably mounted on said body; and means serving to actuate said clampin means and operable by the rotation of sai cover. i

2. In an electrical connecting plug, .the combination of contacts; ciamaing means for connecting the ends of e ectric cable in conducting relation with said contacts; a body housing said clamping means; a cover rotatably mounted on said body; and a cam t'ormcd on said cover and arranged to clamp and release said terminals as said cover is rotated.

3. In a jack plug, the combination of a lip Contact; a sleeve contact; a body on which said contacts are mounted; connectors mount-ed in opposed spaced relation within said body and respectively connected with` said tip and sleeve contacts; and a single cam movably mounted in said body between said connectors, and operable to clamp the insert/ed terminals of a conductor cable against said connectors.

4. In a jack plug, the combination ot a tip contact; a sleeve contact; a body on which said contacts are mounted; connectors mounted in o posed spaced relation Within said body and respectively connected with said tip and sleeve contacts; and a single cam rotatably mounted in said body between said connectors and operable to -cian'ip the inserted terminals of a conductor cable against said connectors.

5. In a jack plug, the combination of a tip contact; a sleeve contact; a two part body havin r a main portion and a ca portion rotatably mounted thereon, sai contacts being' mounted on said main portion; two terminal clamps mounted in said main portion and electrically connected with respective contacts; and a cam rotatable by the rotation of said can portion and mounted between said terminal clamps so as to operate the two simultaneously.

In testimony whereof I have signed my name to this specification.

THOMAS WATTS KIRKMAN.

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